Field of the Invention
The present disclosure relates to a zoom lens and an image pickup apparatus including the same, and is suitable to an image pickup apparatus using an image pickup element such as a digital still camera, a video camera, a monitoring camera, and a broadcast camera, or an image pickup apparatus such as a camera using a silver-halide photographic film.
Description of the Related Art
Recently, functions of image pickup apparatuses such as a monitoring camera and a video camera using a solid-state image pickup element have been advanced, and the overall sizes thereof have been reduced. Zoom lenses used for these apparatuses are required to have a small size, a high zoom ratio, and excellent optical performance. In addition, the zoom lenses are required to have a wider view angle in order to enable one image pickup apparatus to perform shooting over a wider range.
A zoom lens is known which includes, in order from an object side to an image side, a lens unit having a positive refractive power, a lens unit having a negative refractive power, a lens unit having a positive refractive power, a lens unit having a positive refractive power, and a lens unit having a positive refractive power, for the purpose of meeting the requirements.
In Japanese Patent Application Laid-Open No. 2005-55625, a zoom lens is disclosed in which a wide view angle is achieved while reducing distortion aberration and astigmatism by locating a negative lens having a strong concave surface to be closest to an object-side end in a second lens unit.
However, with the zoom lens disclosed in Japanese Patent Application Laid-Open No. 2005-55625, it is difficult to sufficiently achieve an increase in magnification and a wide view angle since magnification varying burdens of the second, a third, and a fourth lens units are relatively small.